Tech Talk

This section is aimed at fellow video and audio producers to share ideas and stimulate discussion. It is not really a 'how to do' guide for beginners.

Multi-cam production for recording seminars and church services .

General:
This article is very much aimed at the 'budget' end of the video spectrum if there is such a thing. How to make stuff that looks reasonably professional without a 5 figure budget. If you find this helpful or you would like to comment then please contact me. I am talking throughout in respect to SD. Although some of the ideas might apply to HDV this is beyond the scope of the article.

Vision Mixers

I was asked to video a series of meetings for Faith Mission. My original intention was to make a number of simultaneous recordings on tape until I discovered there were 16 meetings 2 hours long and I realised that my plan just wasn't feasable. For this reason I started looking at 'as live' recording using a vision mixer. To begin with I aquired an old second hand Panasonic MX10. This only had two channels so the next move was to buy an Edirol V4. This immediately increased the channel count to 4 but it was not a great success. The Edirol can only synchronise cameras on opposite banks so cutting between channels on the same bank is not possible. To do this with the Edirol necessitates you fading between sources for every scene change. This is quite a limitation and is operationally confusing. If you forget and press the wrong button you get a picture disturbance. The Datavideo SE500 proved much better allowing cutting between cameras on the same bank as well as being able to fade etc. It also has a 'quad' preview screen output which is very useful for monitoring. It does have a sound mixer 'built in' although this is only barely adequate. It is unbalanced with no phantom power yet only electret style mics have anywhere like enough level to provide sufficient output.That said this is a grand little mixer and is my clear favoutite for this kind if work.

Monitoring
For multi-cam you need to be able to check that the cameras have a consistent colour balance and if you are using manual exposure, that this is correct. Now even a half decent TV gives you some idea although 'tellys' can be more contrasty and don't always have the controls available to set them up properly. They are big though and it is usually more convenient to use some form of flat screen device. I have found the £100 7 inch LCD monitors no use for serious monitoring. You really need to buy one of the more expensive Teletest or Datavideo monitors for this purpose. One alternative I am trying out is using a Hauppauge HVR900 win tv card to allow me to use my lap top for monitoring. There seems to be some LF noise in the blacks I haven't got to the bottom of yet but it is still gives a very useful picture much more like a tube monitor than cheap LCD screens. For sound level monitoring I use special metering software here inputting audio to the laptop with a Behringer UCA202 interface. The Behringer Minmon is useful as a headphone monitor and for switching between sources.

Recording
Getting the best solution for this was the fruit of a number of very painful and frustrating lessons.

Tape:
When I started out I only had a Sony Video Walkman, so that was the recording solution. First thing I discovered was that the Walkman simply wasn't up to recording in LP mode. I then discovered that any drop-out on the tape had disasterous consequences for audio sync. In the event of a drop out some packages like Premiere 6 continue to capture but the audio is out of sync. Other packages such as Liquid Edition simply mute the audio (without telling you why of course) if a drop-out occurs. The solution? Well one is to get the tape deck frequently serviced but the other one is to take the composite or S-video output of the deck and recapture it using a stand-alone DV bridge such as Canopus ADVC110 or similar. Is there any signal degradation? Well not that I can see on the type of material I am recording.

If you are comitted to going down the tape route then something like this JVC machine would probably be a good way forward. By taking the full size DV tapes it would give the recording time required and the more professional mechanism a more relaible performance than domestic units.

DVD Recorder
At Faith Mission we use DVD as the primary (and only) recorder, I use it for back-up for my mobile work. Advantages are it is simple and easy and pretty reliable. Just remember to select the correct source! I have found it very easy to get audio distortion on the Panasonic models I have used. You need to make sure that the audio levels are not too high. Also make sure the disc is clean. I once put a blank disc down on a surface with a small sticky foreign object on it that transferred to the disc which subsequently stopped the recording.

For editing it is in theory it is possible to 'rip a DVD disc' and place files directly on the time line but beware - these are MPEG2 files which have key frames. If you make edits on a non-key frame there will be some sort of disturbance. I have had difficulty ripping off the third and successive file on home burned discs. I don't know why this is.
The alternative is to play the video back from the DVD player and capture it as analogue video. For some reason this can cause a slight flicker so not really ideal. A further approach is to use DVDRAM on machines (Panasonic) which support it. Panasonic provide specal software for this task. I have experimented with but not gone down this road..

Using a Hard Disc Recorder
For me this is the dream multi-cam recording solution. 2 minutes to boot up. Press record, press stop. Take the drive out and plug it into the computer and edit. Recording on tape means that all the footage has to be captured or digitised later. If there are 30 hours of material to digitise later it is a considerable saving in time to be able to miss out this stage. There are also no tape changes at awkward moments. I am using the Datavideo DN-300R. It has the advantage already mentioned that the hard drive is removeable. For on-camera use, the Firestore FS-4 is popular but it has more limited connectivity and storage capacity.

 

 

 

Direct recording to hard disc Using a Computer
Initially I used my laptop for recording. Now it is possible to use the 'capture' programme with your edit software to do this but it has some limitations. I have found the basic capture programmes with programmes like Premiere 6 and Liquid Edition somewhat temperamental and very easy to loose what you thought you had captured. Not what you want for live recording! At that time a software called DV rack was available at a good price and it was very good. It gave not only a good method of recording but also an excellent method of monitoring. You could set up the colour display on your lap-top (assuming your lap top is hot enough to run it) with both black and white PLUGE so it is very easy to see whether you have got black or white crushing. The software is also fairly reliable for recording. This used to be relatively affordable but now it has been bought out by Adobe and bundled into Premiere Pro (as 'On Location')- if you don't want to buy Premiere Pro it makes it an expensive purchase. What is worse, it now appears that Adobe no longer provide activation for the earlier Serious Magic Product so if you need to reinstall you have had it!

The other issue is external hard drives. Now USB2 apears to be fast enough by specification but for video it just doesn't seem to be reliable for capture. The other options are Firewire or ESATA. Now looking at ESATA first: For a desk-top this would seem ideal as you can achieve phenominal data speeds as the esata lead plugs straight into the SATA sockets on the Motherboard. If your laptop doesn't have an esata port however and you need to use an adaptor, it is a different matter. Without going into the details of the drama shall we just use the word flakey. So we are down to Firewire. And a further word of warning. It is better to have a lap-top with a firewire port. Guess what - if you use a firewire port on an adaptor card it doesn't seem to work. Daisy chain the drive and the dv bridge. You obviously need to buy a firewire drive with 2 ports. Firewire drives can come with 4,6 or 9 way connectors. You need the right leads to match!
But even when you do all this you can still have problems, unexpected stoppages, difficulty in mounting drives. There is really a lot to be said for recording on the Laptop primary drive and then dumping to an external drive later.

In fact there is really a lot to be said for not doing this at all and buying the Datavideo box!

Final comment. No method of recording is 100% reliable. Even the BBC make back up recordings with their £30K machines! My current rig uses the DN300R with a DVD recorder back-up.

Cameras

There are two approaches here. One is to use a 'conferencing' camera such as the EVI D31. The advantage of these is that they can pan and zoom very quickly and I know people who have used them. It is however a single chip camera and the picture quality is not as good as the best three chip camcorders. These are now discontinued but quite widely available on ebay.

 

The other is to use a camcorder on a remote control head (The only affordable one I have come across is sold by Hague). I personally use a semi-pro Sony VX2000 which has good low light sensitivity. Getting a bit long in the tooth now although fairly readily available on Ebay. Most cameras look OK with good lighting but unless you go to a lot of trouble, lighting is usually pretty poor and if the camera is not that great then the result looks awful. The disadvantage of the Hague head is that it is very slow in comparison to the conferencing camera. I use a tone system to control my cameras avoiding the use of long multi-way cables. The DTMF tones are genererated by a standard telephone-style key pad. The decoder is contained in the plastic box beneath the pan and tilt head in the picture, the Lanc controller for the zoom control is also in this box. There are 4 relays in the box to control the Hague head and a further 2 to control the lanc. (If you are interested in this then contact me for further details). The audio tones travel down a standard computer network cable (read on)

 

Video over CAT 5

A very effective way of connecting cameras to either a central monitoring and control point for multi cam recording for later editing or for live switching is to use CAT 5 computer cable and suitable baluns for end connection. The baluns are totally passive so do not require power. This technology relies on the fact that modern computer network cable exceed the performance of conventional video cables.There are several advantages:
The cable itself is light and cheap.
It is possible to get baluns that will accomodate up to two audios and two videos.
It is easy to quickly extend the cable.

A typical application would be to carry monitoring video down the video and have two way talk back down the audio. I would point out that this only works with a fairly 'low tech' talkback system feeding line level audio in both directions. Sophisticated TB systems with bespoke signalling arrangements don't seem to work.
I use an inexpensive headphone amp from Keene Electronics and use the camera microphone for reverse TB. In my application I send DTMF tones down the 'send' audio and feed the video from the camera to the vison mixer. CAT 5 Patch cords can be bought in various lengths up to about 25 metres. I have a colleague with a 300 metre drum of installation cable with RJ45s fitted on each end. It is also possible to get Canon style cables that look like XLR mic cables but have an RJ45 in the shell (Called Ethercon). These are more rugged but you still need an adaptor cable to get into the balun as you also need the matching ethercon chassis connector.

Backgrounds

Where possible I try to use the existing background although this can be a trial. Blue seems to work well but a magnolia wall never seems to look right! The best answer is sky blue curtains that someone else has hung and ironed! Church halls are often cluttered with hat stands and half height acoustic screens which look pretty awful. We take our own curtain kit to such locations. I originally bought a 3 metre long and 3 metre high stand arrangement via Ebay. Unfortuneately the tripods proved very flimsy. I still use the 3 part rod that supports the curtains but I have now bought a pair of Doughty Club 35 lighting stands for the uprights. You can use a length of bathroom tube (the type used for shower rails and towel rails etc) from B and Q. Unfortuneately this only comes in lenghts up to 1.7 metres or thereabouts which is a bit on the short side. Try to get a curtain material that doesn't crease too badly. If you go for a dark colour you will need to forever operate on manual exposure as faces will be over exposed.

Lighting
When averagely bright projectors are being used it is a challenge to light the speaker and not swamp the screen. I use the Karat 60 lighting kit from Karlu Photographic. This uses 70 watt flourescent coil bulbs in an unbrella reflector. There are more powerful versions available with equivilent power output of 500W and 1000W!

Handling Powerpoint
To incorporate powerpoint into the video some form VGA to PAL converter is required. These vary in sophistication. It is helpful to have one where the image size can be adjusted if that is available. The units usually allow pass-through of the VGA signal but we have found that if the VGA feed to the projector is very long or if projectors are daisy chained or both, then operating in pass through mode can be the last straw and we have found it necessary to use a splitter box at the laptop.

Editing
My personal choice is Liquid Edition. This is historically because it was ahead in the multi-camera editing at the time. I haven't recently investigated other packages for comparison. Adobe premiere Pro has its enthusiasts and it is ultimately compatible with other Adobe applications such as Aftereffects. Edius is also popular. For Mac, Final Cut pro is the ultimate choice but you need to make sure your Mac runs the latest version of the software.

Producing Internet compatible files
There are a number of issues regarding internet compatible files. One is where you are going to post them. Another is the platform they will be played on - Windows or Mac. Yet another is whether they will 'stream' -ie start to play as soon as they start to down-load. For Free hosting on the Vimeo web sites we use H264 files which are encoded as MPEG 4. Now MPEG 4 encoders seem to vary. The one which is bundles with Liquid Edition doesn't work very well for me. We have found the best solution is to use a freeware programme called Handbrake. Because this software is designed to convert DVDs to files for portable devices you need to have a DVD to start with. So the production process is to edit in DV. Encode to MPEG2. Burn a DVD. Encode to MPEG4. Upload. Seems very roundabout but it works better than encoding to MPEG 4 directly. A note about Handbrake. It produces files with an .M4v file extension. This needs renaming to an .MP4 extension before it can be uploaded. I have also had trouble uploading long Vimeo files with the 'free' application. This problem totally goes away if you upgrade to the Vimeo Plus application for £60 per year. What a surprise!

Video Trolley

This is my current version of my video trolley based on the SKB Mini Gig Rig. It is not totally ideal for this job but I happened to have one. The trolley is dual purpose inasmuch as it is designed to work totally remote control using the DTMF panels or with camera men using the TB and reverse TB functions. Two flat screen monitors are on the fold flat screen at the top. The left hand one is a Datavideo quality monitor which can show the 4 preview screens or the output of the Datavideo DN300 recorder. The RH monitor is a cheapo 8 inch monitor which shows the output of the DVD recorder. Must bite the bullet at some stage and replace this with a second Datavideo monitor. Below that is the Datavideo SE500 video switcher and on the top panel are the TB buttons and reverse talk-back mixer. To the right are the tone keypads to drive the pan and tilt head and zoom control.

Below is the Panasonic DVD recorder and the VGA to PAL scan convertor. Below again is the Minmon monitor box and the Datavideo DN300.

Finally at the bottom is the connection panel. (With radio mic receiver in front.) The next development is to move the connection panel up to the top and behind the monitors as it is difficult to get the VGA cables in and out (for recording powerpoint) and a nuisance to have all the cables around the operators feet.

Not shown on the photo are some big soft 5 inch wheels I found on Ebay which are a major improvement on the 4 inch hard nylon ones on the mark 1 version of the trolley

Edited 18th december 2009